Extracorporeal life support equipment is used during extracorporeal cardiopulmonary bypass to mechanically perform the functions normally performed by the heart and lungs. The venous blood, which is depleted in oxygen and rich in carbon dioxide, is mechanically removed from the patient via medical catheters and connecting tubing and pumped to oxygenating apparatus. The oxygenated blood is later returned to the patient's arterial system via further medical tubes and medical catheters.
The medical catheters used to drain the venous blood are generally known as venous return catheters. U.S. Pat. Nos. 4,639,252 and 4,129,129 describe such catheters to be of a single or of a dual drainage construction. The dual drainage construction includes drainage openings at the distal end and also along the catheter's length proximal to the distal end. This is known to many times eliminate the need for a second catheter requiring a second entry incision or wound in the wall of the heart. Dual-drainage catheters are typically inserted through the right atrium and into the inferior vena cava with the proximal drainage openings positioned within the right atrium. This placement permits blood to be drained simultaneously from the vena cava in which the dual-drainage catheter is placed and from the right atrium.
As noted in the foregoing patents, it is exceedingly important that adequate volumes of blood be drained from the patient during cardiopulmonary bypass so that the extracorporeal life support equipment can keep up with the patient's need for oxygen and can adequately remove excess carbon dioxide. Insufficient quantities of oxygen can lead to serious tissue damage.
As pointed out in U.S. Pat. No. 4,639,252, some surgical procedures require manipulation or movement of the heart. Since the inferior vena cava is substantially anchored in place, manipulation of the heart frequently increases the angle of bend in the portion of the catheter situated at the juncture between the inferior vena cava and the right atrium. Not uncommonly, according to this patent, the increased degree of bending causes the catheter to become kinked. This is said to restrict or even interrupt blood drainage from the inferior vena cava.
The dual-drainage catheter described in U.S. Pat. No. 4,639,252 is reinforced in the area of the proximal drainage openings to minimize such kinking. This reinforcement is described as a reinforcing member 24 in the form of a layer of 90 Shore A durometer polyvinyl chloride material having a thickness of about 1 millimeter with the proximal drainage openings being punched through this layer.